Many hydraulically actuated fuel injectors utilize a poppet valve to regulate flow of actuation fluid into a control chamber. This poppet valve is moveable between a high pressure seat and a low pressure seat. When the poppet valve is seated at the high pressure seat, a drain is opened to the control chamber of the injector and an actuation fluid inlet is closed. The poppet valve is biased toward the high pressure seat between injection events by a biasing spring. At the beginning of the injection event, the solenoid is energized and the armature pulls the poppet valve upward away from the high pressure seat against the action of the biasing spring and toward the low pressure seat. When the poppet valve closes the low pressure seat, high pressure actuation fluid can enter the control chamber of the fuel injector to commence an injection event.
While these fuel injectors have performed magnificently, there is room for improvement in their design. The poppet valve is rigidly attached to the armature of the solenoid such that they are designed to behave as a single rigid body. The performance of the poppet valve is related to a small air gap between the armature and the solenoid coil. With each injection event, the same surfaces of the poppet valve are continually striking the high and low pressure seats. Because the opening and closing takes place many times per second, the poppet valve contacts the high and low pressure seats with a relatively high impact velocity. Because the same surfaces of the poppet valve are impacting the high and low pressure seats with this high impact velocity, these surfaces tend to wear, causing a change in the initial air gap. As this change in the dynamic relationship between the armature and the solenoid coil occurs, there is a change in the performance of the injector. Because each injector wears differently, the performance diverges over the life of individual injectors.
Because proper operation of the poppet valve relies on several stacked tolerances, there is a tendency for individual injectors to perform within some acceptable range of performance. While some performance variations between individual injectors initially is inevitable because of the large number of components, engineers are always seeking a reduction in the initial range between individual injectors.
The present invention is directed to overcoming one or more of these problems set forth above.